In the U.K. you should email 999testcalls@bt.com first, although strictly speaking for a one off test (typically by an end user rather than a professional) it’s

In the U.K. you should email 999testcalls@bt.com first, although strictly speaking for a one off test (typically by an end user rather than a professional) it’s ok to just call and explain. https://www.ofcom.org.uk/phones-and-broadband/telecoms-infrastructure/telecoms-industry-guidance https://www.ofcom.org.uk/phones-and-broadband/telecoms-infra...